Some computer systems include fault tolerant components. For example, a computer system may include a main power supply and a backup power supply. The backup power supply (also referred to as the battery backup unit of the computer system) powers the computer system for a period of time in the event the main power supply no longer powers the computer system (e.g., due to an external or internal power outage). That is, when the main power supply no longer powers the computer system, detection circuitry within the computer system (i) directs the backup power supply to power the computer system, and (ii) prompts the computer system to perform an emergency de-stage procedure. In response, the computer system continues operating until it reaches a safe stopping point (e.g., completes its current tasks, synchronizes volatile memory with non-volatile memory, closes files, etc.) and then shuts down in a controlled manner.
A typical backup power supply includes a set of charged batteries (or cells). Sealed lead-acid (SLA) batteries are commonly used in backup power supplies. In one configuration, as long as the main power supply remains in operation, the main power supply periodically charges the batteries. This prevents the batteries of the backup power supply from losing their charge over time.
Nevertheless, as the batteries of the backup power supply age over time, one or more batteries of a backup power supply may lose its ability to provide suitable charge (typically measured in units of Ampere-hours or Ah) to power the computer system long enough for the computer system to properly complete its tasks and shutdown. Accordingly, technicians periodically test backup power supplies.
There are two conventional approaches to testing a backup power supply: the open circuit voltage test approach and the forced online discharge approach. In the open circuit voltage test approach, the technician measures the output voltage of the backup power supply while the backup power supply is not being charged. If the backup power supply is configured to receive charge from the main power supply, the technician separates the backup power supply from the main power supply, and then attaches a volt meter across leads of the backup power supply. If the output voltage of the backup power supply is equal to or higher than a predetermined threshold (e.g., 50 volts), the technician concludes that the backup power supply operates properly and allows the backup power supply to continue backing up the main power supply. However, if the output voltage is less than the predetermined threshold, the technician concludes that the backup power supply is faulty and requires replacement (i.e., concludes that the backup power supply will not be able to properly power the computer system in the event the main power supply no longer powers the computer system).
In a first version of the forced online discharge approach, the technician disconnects or deactivates the main power supply (e.g., unplugs the main power supply from the main source, turns off the main power supply, disconnects the main power supply from the computer system, etc.). If the backup power supply operates properly, the backup power supply powers the computer system (in response to control signals from detection circuitry) enabling the computer system to properly complete its current tasks and shutdown. However, if the backup power supply is incapable of adequately powering the computer system, the computer system stops abruptly or crashes due to the lack of power thus signaling the technician that a replacement backup power supply is required.
In a second version of the forced online discharge approach, the technician lowers the output voltage of the main power supply (e.g., from 56 volts to 42 volts) and prevents the main power supply from providing charge to the backup power supply. The technician then allows the backup power supply to power the computer system (i.e., discharge through the computer system) while measuring the output voltage of the backup power supply in order to determine whether the backup power supply operates properly. A gradual drop in output voltage indicates that the backup power supply operates properly, but a quick drop in output voltage indicates that the backup power supply does not operate properly.
Unfortunately, there are deficiencies to the above-described conventional approaches for testing backup power supplies. For example, in the conventional open circuit voltage test approach, the backup power supply may pass the output voltage test performed by a technician. That is, the backup power supply may provide an adequate output voltage, i.e., an output voltage that is higher than a predetermined threshold, when a technician tests the backup power supply. However, the backup power supply may be incapable of powering the computer system for an amount of time necessary for the computer system to complete its current tasks and shutdown. One reason is that batteries within the backup power supply may have a float charge that is capable of sustaining an output voltage that equals or exceeds the predetermined threshold for less than a few seconds. Accordingly, the backup power supply may appear to be fully charged and seem as though it possesses the capacity to power the computer system for a substantial time period in the event of a power loss when, in reality, the backup power supply can only power the computer system for a few seconds. In particular, once the float charge is removed (e.g., after the backup power supply powers the computer system for a few seconds), the backup power supply provides little or no charge. As a result, in the event the main power supply no longer powers the computer system, the backup power supply may power the computer system for a short period of time (e.g., a few seconds) before the computer system crashes (i.e., before the computer system can complete its current tasks and shutdown properly).
In the first version of the conventional forced online discharge approach, the computer system drains the charge on the backup power supply. The computer system then either remains in operation to complete its current tasks and properly shut down in a controller manner if the backup power supply is good, or crashes if the backup power supply is faulty. A computer system crash is an undesirable situation and is generally perceived as a catastrophic malfunction since computer systems can sustain damage when abruptly powered down in an uncontrolled state. For example, a head disk assembly may inadvertently corrupt or erase important data on a disk if the disk is allowed to operate in an uncontrolled state and the power supply is abruptly removed. As another example, a computer system may lose valuable information stored in volatile semiconductor memory (e.g., a RAM memory cache) which has not yet been synchronized to non-volatile disk memory).
In the second version of the forced online discharge approach (e.g., dropping the output voltage of the main power supply from 56V DC to 42 V DC and preventing the main power supply from charging the backup power supply), the main power supply eventually powers the computer system once the output voltage of the backup power supply drops to the same output voltage as that provided by the main power supply. When this occurs, a tremendous stress is placed on the main power supply since the main power supply attempts to provide the same power or wattage to the computer system by substantially increasing its output current. In particular, the quantified current stress is the squared ratio of currents (computable using voltage values), e.g., (56V/42V)2 equaling (1.333)2 or 1.777, which is considered too high a stress to place on the main power supply for testing the backup power supply in the field. Such stressful operation risks heavily damaging the main power supply, as well as risks crashing the computer system if the main power supply burns out. Accordingly, the second version of the forced online discharge approach is a poor approach for testing the backup power supply.
In contrast to the above-described conventional approaches to testing a backup power supply, the invention is directed to techniques for testing a powerability characteristic of a backup power supply for a computerized device using a discharge circuit that is different than circuitry of the computerized device. The discharge circuit is capable of draining the float charge of the backup power supply thus enabling a measuring circuit to subsequently determine whether the backup power supply is suitable for providing operating power to the computerized device for a predetermined amount of time in the event the computerized device no longer receives main power from the main power supply. Such techniques are sufficient to discover even one malfunctioning or xe2x80x9cemptyxe2x80x9d cell masked by float charge within a backup power supply (e.g., a battery backup unit) containing several cells (e.g., 24 cells).
One arrangement of the invention is directed to a computer system that includes a computerized device, a main power supply that provides power to the computerized device, and a backup power supply coupled to the main power supply to receive charge from the main power supply. The backup power supply provides operating power to the computerized device for a predetermined amount of time in the event the computerized device no longer receives main power from the main power supply. The computer system further includes an apparatus that tests a powerability characteristic of the backup power supply (i.e., the capacity to power the computerized device for a predetermined time period). The apparatus includes a discharge circuit that connects to the backup power supply, and that is different than circuitry of the computerized device. The apparatus further includes a measuring circuit that measures, when the backup power supply is connected to the discharge circuit, an amount of time that the backup power supply provides an output signal meeting a predetermined criterion in order to determine whether the backup power supply is suitable for providing operating power to the computerized device for a predetermined amount of time in the event the main power supply no longer powers the computerized device.
In one arrangement, the discharge circuit includes a heating coil assembly that, when connected to the backup power supply, forms a closed circuit with the backup power supply. Preferably, the discharge circuit further includes a fan assembly that, when connected to the backup power supply, forms a closed circuit with the backup power supply such that the fan assembly provides an air stream across the heating coil assembly to cool the heating coil assembly.
In one arrangement, the measuring circuit includes a voltage detection circuit, and a computer coupled to the voltage detection circuit. The computer is configured to record an amount of time the backup power supply powers the discharge circuit while the backup power supply provides an output voltage that exceeds (or equals) a predetermined voltage threshold (e.g., 50 volts). In this arrangement, the output voltage provided by the backup power supply is the measured output signal of the backup power supply.
In one arrangement, the computer includes memory having a database that stores amounts of time for other backup power supplies powering discharge circuits while the other backup power supplies provide output voltages over the predetermined voltage threshold, and a processor coupled to the memory. Accordingly, the computer can be configured to collect data regarding backup power supply performance for subsequent testing refinement and development.
In one arrangement, the computer is configured to record a first time measurement when the discharge circuit connects to the backup power supply and when the output voltage of the backup power supply exceeds the predetermined voltage threshold, and record a second time measurement when the output voltage no longer exceeds (or equals) the predetermined voltage threshold. The computer is configured to then generate a difference between the first and second time measurements. The difference is an amount of time the backup power supply powered the discharge circuit while the backup power supply provided an output voltage over the predetermined voltage threshold.
The features of the invention, as described above, may be employed in computer systems, tests devices and procedures, and other computer-related techniques such as of EMC Corporation of Hopkinton, Mass.